Sensor material for use in detection of electrically conductive fluids

ABSTRACT

Apparatus for detecting the presence of electrically conductive fluids, including urine and other body fluids such as exudate from wounds, includes a pair of spaced-apart electrodes covered by absorbent material, together with a housing containing a signaling device which produces a palpable vibration, a sound, a light, or a radio signal when fluid in the absorbent material provides a conductive path between the electrodes. Spring contacts on the housing provide reliable connections with the electrodes and also serve to attach the housing of the signaling device to structure supporting the absorbent material, and may also be used to attach the absorbent material to the housing in embodiments where the housing is otherwise supported. Disposable sensing pad material which is comfortably soft and flexible can be produced in indefinite lengths with moisture-previous outer layers and an inner layer of absorbent thermally-weldable material. Encoded signals from many such sensors can be identifiably related to and recorded so as to be machine-retrievable together with other patient data and analyzed statistically by a computer.

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/104,122, filed Jul. 20, 1993, now U.S. Pat. No. 5,557,263,issued Sep. 17, 1996, which is a continuation-in-part of U.S. patentapplication Ser. No. 07/918,273, filed Jul. 22, 1992, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to detection of electrically conductivefluids, and in particular to detecting and signaling the release ofbodily fluids from human beings or animals.

For many years the objective of electrically detecting and indicatingthe presence of body fluids or other electrically conductive liquids hasbeen pursued. Detecting such fluids often has involved using a pair ofelectrodes connected with a voltage source and a detector circuitintended to turn on an audible alarm when a gap between the electrodesis bridged by an electrically conductive fluid.

Devices for detecting body fluids are desired particularly for assistingin the prevention of diaper rash, for potty training of infants, and incuring enuretic youngsters, as well as for detecting the leakage ofblood or other fluids after surgery and invasive diagnostic procedures.Such devices are also desired to monitor and record urinary incontinenceand to facilitate better care for pressure sores in chronicallybedridden persons.

Previously available devices for use to detect human body fluids havemany disadvantages. For example, some prior art devices are too bulkyand uncomfortable for use in the groin area for monitoring urinaryincontinence. Some prior art devices use cumbersome and unsafe longelectric wires to interconnect the necessary component parts.

Other drawbacks of previously available devices include sensors whichare too large or too small, are not shaped properly, or are made ofmaterials which are not compatible with the human body or other intendedenvironment. In particular, prior art devices have not satisfactorilyprovided for early detection of small amounts of body fluids. Also, manyprior art devices are too expensive to manufacture economically or areimpractical to use.

What is desired, then, is a system including an improved sensor and anassociated alarm system for reliably and consistently detecting andsignaling the presence of electrically conductive fluids under allconditions of use, without false alarms. Such a sensor should be ofsmall size, comfortable to use, easy to maintain, clean, and prepare forreuse, self-powered, and portable. Preferably, a system incorporatingsuch a sensor should have the ability to provide signals to remotemonitors for collection and analysis of data, and should be simple touse.

SUMMARY OF THE INVENTION

The present invention provides improved apparatus and a method for itsuse to overcome the aforementioned shortcomings of the prior art and, inparticular, provides an improved, simple, and versatile device forsignaling the presence of electrically conductive fluids, such as urine,wound exudate, feces, blood, and water, and also provides a disposableabsorbent pad for use in detecting such electrically conductive fluids.

An important feature of one embodiment of the present invention is theuse of comfortable, soft, nonabsorbent material to support an absorbentsensor and a housing for a signaling device including an electricalcircuit which form parts of the device.

In one embodiment of the invention a fluid-absorbent sensing pad has twoapart-spaced electrodes, included in the structure of the absorbent padand available to be connected electrically to the signaling device.

One embodiment of the invention provides a sensing pad of soft,flexible, liquid-absorbent material, whose design and shape providecomfortable positioning and detection of even very small amounts of bodyfluids for either male or female users.

It is a feature of one embodiment of the present invention that thefluid-detecting electrode system is compatible with different signalingdevices that provide vibratory, audible, visible, or wireless signals.

One embodiment of the invention provides a disposable fluid-absorbentsensor material which can be manufactured efficiently as a continuousroll that can be cut to a desired length and which is soft and flexibleenough to be worn in comfort.

One embodiment of the invention includes a radio transmitter and anencoding device for sending a signal which is identifiably encoded forreception and interpretation by a remotely located receiver, which maybe portable.

In one embodiment of the invention encoded information may includeidentification of the source of the encoded signal, while equipmentassociated with the receiver can record the received signalidentification information as well as time of receiving a signal, andcan then compute elapsed time since an earlier signal was received, andother information.

One embodiment of the invention includes the use of an FM radiotransmitter which transmits on the commercial FM broadcast frequencyband. Signals from such an FM transmitter can be received byconventional domestic radio receivers, enabling most users to have morethan one remote receiver.

The invention also provides a method of manufacturing a disposablesensor strip by providing an elongate sheet of material including anabsorbent layer and a fluid previous layer, attaching a pair ofelectrodes to the sheet parallel with each other and on opposite sidesof a central portion, and folding the strip to bring lateral marginstogether and fastening them to the central portion, thereby defining apair of parallel tubes each having an inner surface and a respective oneof the electrodes attached to the inner surface.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a bed-wetting detection device embodying thepresent invention.

FIG. 2 is a sectional view of the device shown in FIG. 1, taken alongline 2--2.

FIG. 3 is a rear view of the carrier assembly portion of the bed-wettingdetection device shown in FIG. 1, together with a portion of anabsorbent sensor pad and a fastener for attaching the pad to the carrierassembly.

FIG. 4 is a perspective view of a housing for electronic components of asignaling device which is a part of the apparatus shown in FIG. 1.

FIG. 5 is a perspective view, taken from the opposite side, of thehousing for electrical components shown in FIG. 4.

FIG. 6 is an electronic circuit diagram for an audio-output alarm whichis part of a signaling device for use in the apparatus shown in FIG. 1.

FIG. 7 is a plan view of an apparatus similar to that shown in FIG. 1and including a belt for attachment of the device to a person.

FIG. 8 is a perspective view of a device for detecting conductive fluidsuch as body fluids which is an alternative embodiment of the invention.

FIG. 9 is a perspective view of a roll of absorbent sensor materialincluding absorbent layers and electrodes, according to the invention,useful as a disposable sensing pad material in detecting electricallyconductive fluids in accordance with the present invention.

FIG. 10 is a sectional view, taken along line 10--10, showing thestructure of the material shown in FIG. 9.

FIG. 11 is a side elevational view of the housing shown in FIG. 8,together with a disposable sensing pad.

FIG. 12 is a view similar to FIG. 11, showing the spring fingers held ina contact-releasing position by a cam.

FIG. 13 is a side elevational view of a detail of a housing similar tothat shown in FIGS. 8, 11 and 12, and equipped with spring fingers whichinclude somewhat different electrical contacts.

FIG. 14 is a view of a contact shown in FIG. 13, taken in the directionindicated by line 14--14.

FIG. 15 is a partially cut-away view of a housing for electroniccircuitry for providing a quiet signal which can be felt by the wearerof a device according to the present invention, including a clip forattachment of the housing to a person's clothing.

FIG. 16 is an electronic circuit diagram illustrating a circuit for usein connection with the vibrator signaling device shown in FIG. 15.

FIG. 17 is a simplified view of a system including a radio transmitterand receiver in combination with a sensor according to the presentinvention for detecting the presence of electrically conductive fluids.

FIG. 18 is a view similar to FIG. 17, showing the use of a receiver inaccordance with the present invention to provide a visible indication ofa signal from a sensing device.

FIG. 19 is an electronic circuit diagram for a portion of a signalingdevice for use in accordance with the present invention, including asignal repeat timer.

FIG. 20 is a block diagram of a system according to the presentinvention including several body fluid detection devices each includinga wireless signaling device.

FIG. 21 is a view of a system monitoring unit and several sensingdevices of a system according to the present invention.

FIG. 22 is a perspective view of a roll of absorbent sensor materialaccording to the invention, including an absorbent layer and electrodes,useful as a disposable sensing pad material for detecting electricallyconductive fluids in accordance with the present invention.

FIG. 23 is a perspective view of a portion of an elongate piece of sheetmaterial which is useful as a component of the absorbent sensor materialshown in FIG. 22.

FIG. 24 is a section view of the absorbent sensor material shown in FIG.22, at an enlarged scale, taken along line 24--24 of FIG. 22.

FIG. 25 is a section view similar to a central portion of FIG. 24,showing an alternative embodiment of the absorbent sensor materialaccording to the invention.

FIG. 26 is a block diagram of a method for manufacturing a sensormaterial such as that shown in FIG. 22.

FIG. 27 is a simplified pictorial representation of the process offorming the sensor material shown in FIG. 22.

FIG. 28 is a simplified illustration of a production machineryarrangement for manufacturing a continuous strip of absorbent sensormaterial according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings which form a part of the disclosureherein, and with particular reference to FIGS. 1-6, an apparatus fordetecting the presence of electrically conductive fluids, in the form ofa bed wetting detector 10, includes a sensor carrier assembly 12 havinga flat, generally rectangular configuration adapted to fit, for example,against the front of a wearer's night clothes as support for thedetector 10. The carrier assembly 12 includes a pair of alligator clips14, one attached at each end, as one way to attach the carrier assembly12 to a person's clothing, such as the elastic waistband 16 of a pair ofunderpants, to keep it in a desired location in which a sensor portion18 is best positioned to receive and absorb urine when the personwearing the device first begins to urinate while sleeping.

The carrier assembly 12 is constructed of a sheet 20 of closed-cellpolymeric foam material which may be 3 mm thick, for example, foldedalong a central slit 22 to define a horizontal bottom 24 of the carrierassembly. A recess 26 is defined on the front part of the carrierassembly 12 by a cutout in the top margin 28 of the folded sheet 20,providing a convenient location for attachment of a housing 30containing electrical circuit components including a signaling device32.

The sensor portion 18 of the device 10 is reusable and includes anelectrode-carrying member 34 in the form of a backing layer of sheetplastic material such as polyvinylchloride 0.50 mm thick having a pairof opposite longitudinal margins, an upper portion of each of whichextends laterally defining tabs 36 to which the alligator clips 14 areattached. The electrode-carrying member 34 may, for example, have alength 38, of about 23 cm overall, with about 18.7 cm depending downwardbelow the central slit 22 in the closed-cell foam material of the sheet20. The depending portion of the electrode-carrying member in apreferred embodiment of the invention is 7 cm wide over approximatelyits upper half, its lower half tapering to a width of approximately 4.5cm at its lower end.

A rectangular piece 40 of flexible plastic material such aspolyvinylchloride 0.25 mm thick extends lengthwise between the oppositehalves of the folded sheet 20 of closed-cell foam material and isattached along its vertical ends to the rear side of the upper portionof the electrode-carrying member 34. The inner surfaces of the sheet 20of closed-cell foam are attached to the flexible plastic material of thepiece and of the electrode-carrying member by an adhesive, such asADCHEM 5008B, available from Adchem Corporation of Westbury, N.Y. Aspace 42, open at its top and bottom is thus defined between the piece40 of flexible plastic material and the upper portion of theelectrode-carrying member 34.

Two parallel, flexible electrodes 44, 46 are attached to theelectrode-carrying member 34 on its rear side, that is, the side facingtoward the body of the user of the device. The electrodes 44, 46 arethus exposed, spaced apart from and parallel with each other, within thespace 42 defined between the piece 40 of flexible plastic material andthe electrode-carrying member 34.

The housing 30 is attached to the carrier assembly 12 by a pair ofspring fingers 48 of resilient sheet metal, each of which iselectrically connected appropriately to the electronic circuitcomponents contained within the housing 30, as shown in FIG. 6, and eachof which also includes a contact portion 50. The resilient springfingers 48 attached to the housing bring each of the contact portions 50into mechanical and electrical contact with a respective one of theelectrodes 44, 46 within the space 42 defined between the flexibleplastic 40 and the electrode-carrying member 34. Preferably, each of thefingers 48 has an upturned tip, to facilitate sliding the housing intoposition with the fingers 48 in the space 42, with each contact portion50 contacting a respective one of the electrodes 44, 46.

Each of the electrodes 44, 46 is a strip of conductive flexiblepolyimide material impregnated with carbon black, such as that availablefrom DuPont Electronics of Wilmington, Del., and known as KAPTON400XC250, which has a suitably low resistivity of 250 ohms/sq. Each ofthe electrodes 44, 46 is approximately 1.3 cm wide, and a spacing 52 ofapproximately 1.1 cm is provided between the medial margins 54 of thetwo electrodes.

Preferably, an additional piece 56 of flexible plastic is attached by anadhesive to the front face of the carrier assembly to protect theclosed-cell foam material of the sheet 20 from possible abrasion by thesurface of the housing 30, and to facilitate removal and replacement ofthe housing 30 from and onto the carrier assembly 12.

An absorbent sleeve 58 fits around the electrode-carrying member 34 andthe electrodes 44, 46, fitting snugly against the bottom 24 of thecarrier assembly 12, adjacent the central slit 22. A flap 60 extendingupward on the rear side of the sleeve 58 carries a small patch 62 of thehook-bearing material of a hook-and-loop fastener system such as thatknown by the trademark Velcro®, while a patch 64 of the loop-bearingmaterial of the fastener system is attached, as by an adhesive, to therear surface of the sheet 20 of closed-cell foam material of the carrierassembly 12, so that mating the two fastener materials 62, 64 holds thesleeve 58 appropriately in position covering the depending portions ofelectrode-carrying member 34 and the electrodes 44, 46.

The sleeve 58 is made of an absorbent material which is preferablywashable, such as a central layer 66 of a batting of polyester fibers,covered on opposite faces by layers 68 of thin, fluid-absorbent clothsuch as a cotton-polyester blend, which may be quilted, with front andrear panels of the resultant three-layer fabric being sewn togetheralong their respective longitudinal margins and bottom margin. Theentire sensor portion 18, including the sleeve 58 and theelectrode-carrying member 34, is flexible but not too bulky to be worncomfortably within a user's underwear.

Referring to FIG. 6, the bed wetting detector 10 includes an audio alarmwhich may be contained as a signaling device 32 within the housing 30.An electronic switch 70, such as a Harris H11A10 photon-coupled currentthreshold switch, in which a solid-state gallium arsenideinfrared-emitting diode is coupled with a silicon photo-transistor in adual in-line package, is connected to provide power from a battery 72 toan audio transducer 74 which may, for example, be a Series AI612electronic solid-state audio indicator unit available from ProjectsUnlimited, Inc. of Dayton, Ohio, capable of providing 90 dba soundpressure at a frequency of about 400 Hz.

When a circuit is completed through an electrically-conductive fluidabsorbed in the sleeve 58 in a location interconnecting the electrodes44 and 46, the current through the electrically-conductive fluid issufficient to turn on the electronic switch 70, providing a current pathfrom the battery 72 through the audio transducer 74, so long as thebattery 72 lasts and the circuit remains intact through the sensorportion 18 of the device. Thus, when moisture, such as a sufficientquantity of urine, completes the circuit the audio transducer 74 willproduce enough noise to waken the person wearing the device 10, usuallya small child, to enable the child to stop urinating and to learn toawaken before wetting the bed. The noise of the transducer 74 can bestopped by simply removing the spring fingers 48 of the housing 30 fromcontact with the electrodes 44, 46 within the carrier assembly 12.

Once the sleeve 58 has been made wet, it can be removed, permitting thecarrier assembly 12, the electrode-carrying member 34, and theelectrodes 44, 46 of the sensor portion 18 of the device, and theexterior of the housing 30, to be wiped dry. Thereafter, the sleeve 58can be replaced with a dry one and the housing 30 can be replaced on thecarrier assembly 12, allowing the bed wetting detector 10 to continue tomonitor the wearer.

Referring to FIG. 7, as an alternative embodiment of the apparatus shownin FIGS. 1-6, a carrier assembly 76 may include, instead of the pair ofalligator clips 14 at the ends of the carrier assembly 12, a belt 78 ofclosed-cell foam material similar to that of the sheet 20 of the body ofthe carrier assembly 12. The belt 78 is equipped with mating patches 80,82 of hook-and-loop fastener material, and excess length of the belt canbe trimmed easily, so that the device can be used with people ofdifferent sizes.

Referring next to FIGS. 8-12, a body fluid detecting device 84 which isanother embodiment of the invention includes a housing 86 for electroniccircuitry similar to the housing 30 previously described. It includes analligator clip 88 attached to the housing, as by a looped strip 90 offlexible plastic material engaged movably through an opening defined bya small strip 92 of plastic material fastened to the housing.

Instead of the carrier assembly 12 and the associated reusable sensorportion 18, however, the body fluid sensing device 84 shown in FIGS.8-12 utilizes a disposable sensing pad 94 of absorbent sensor material95 which includes a pair of electrodes 96, 98. The absorbent sensormaterial of the disposable sensing pad 94, as shown in FIGS. 9 and 10,has the form of an elongate strip and may be provided in the form of aroll of such material 95 which can be cut to a desired or requiredlength. For example, for use to detect urinary incontinence, a strip ofthe absorbent sensor material 95 may be cut approximately the samelength, in the direction indicated by the arrow 100, as the length ofthe electrode-carrying member 34 of the reusable sensor 18 describedpreviously, or to a shorter or longer length, depending upon the size ofthe person using the device.

Two strips 102 of an adhesive material, normally covered by an easilyremovable protective paper tape 104, are available on one face of thedisposable sensing pad 94, to be used to attach the disposable sensingpad 94 to a person's clothing. Where the device is used to detectseepage from a wound, the adhesive material may be used to attach theabsorbent sensor material 95 to person's skin, instead, or to a portionof a bandage, as appropriate. An adhesive material such as thatavailable in the form of a spirally rolled strip of adhesive and aprotective paper layer from the Minnesota Mining and ManufacturingCompany of Minneapolis, Minn., as its No. 924 adhesive is suitable,although an adhesive applied in fluid form and then covered with theprotective paper tape 104 during the process of manufacture of theabsorbent sensor material 95 would also be suitable.

The absorbent sensor material 95 of the disposable sensing pad 94 is ofmulti-layered construction, including a pair of inner layers 106, 108 ofa continuous, absorbent soft paper or similar material having a width110 of about 4.5 cm. The pair of flexible electrodes 96, 98 may beribbon-like strips of polyester plastic provided with a conductivemetallic coating, such as aluminum, on each face, and are attached bylayers 112 of an adhesive to the sheet 108 of paper, with one metallizedface of each electrode facing away from the sheet 108. The closer, ormedial, longitudinal margins 114 of the electrodes are spaced apart fromone another by, a distance 116 of, for example, 1.2 cm, and eachelectrode has a width 118 of 1.2 cm, leaving three to four tenths of acentimeter of the width 110 of the paper clear alongside the outer orlateral longitudinal margin 120 of each electrode.

The other sheet 106 of the absorbent soft paper overlies the sheet 108to which the electrodes 96, 98 are adhesively attached, and the twosheets 106, 108 of absorbent paper are attached to each other by strips122 of adhesive material along their longitudinal margins, and byadhesive material, preferably in the form of a continuous strip 124,located between the two electrodes 96, 98 to prevent them from beingpushed into contact with each other as a result of the disposablesensing pad 94 bending to conform to a person's body or clothing duringuse of the device.

On each side of the disposable sensing pad 94 an outer layer 126 or 128of flexible fluid-conducting absorbent material overlies the innerlayers 106, 108. The outer layers 126, 128 are attached to each otherand to the margins of the inner layer of material, as by adhesivematerial 130 interconnecting the longitudinally-extending lateralmargins 132 of the outer layers with each other and also attaching theouter layer 128 to the inner layer 108, to which the electrodes 96, 98are adhesively attached. Instead of the adhesive materials 112, 122, 124and 130, ultrasonic welding may be used to bond together the inner andouter layers 106, 108, 126 and 128 if a weldable bonding agent, such aslatex, is included in the materials of the inner or outer layers.

Each electrode 96, 98 is exposed within a respective tube 134 formed bythe opposing surfaces of the inner layers 106, 108 of absorbent softmaterial. The spring fingers 136 on the outside of the housing 86, eachelectrically connected appropriately with the electrical componentscontained within the housing, fit within the tubes 134. The contacts 138located on the spring fingers 136 thus make electrical contact with theelectrodes 96, 98, while the electrodes 96, 98 are kept separate fromeach other by the bonded-together portions of the inner layers 106, 108.

The inner layers 106, 108 may, for example, be of a paper productavailable from Fort Howard Paper Company of Green Bay, Wis. as its grade835 dry form 8-ply lightweight fabric made of bleached pulp. The outerlayers 126, 128 may be of a rayon apertured fabric, print bonded with arope pattern, and available from Fort Howard Paper Company of Green Bay,Wis., as its grade 920 Carded™ material. The material of the outerlayers 126, 128 has a lower absorbent capacity but a higher wet tensilestrength than the material of the inner layers 106, 108, so that theouter layers provide strength to the disposable sensing pad 94 and allowmoisture to pass quickly to the inner layers 106, 108 to be absorbed andbrought into contact with the electrodes 96, 98 to complete anelectrical path between the electrodes.

As shown in FIGS. 8, 11 and 12, the spring fingers 136 includedown-turned tips as the contacts 138, to provide electrical contact withthe electrodes of the absorbent sensor material 95 of the disposablesensing pad 94. The spring fingers each include a zigzag bend, and thehousing 86 includes a raised ridge 140 defining a support for a cam 142which can be rotated toward the zigzag bend by a lever 144 to raise thecontacts 138 away from the housing 86 to permit the ends of the springfingers 136 to be inserted into the tubes 134 of the disposable sensingpad 94. When the lever 144 is returned to a position parallel with theouter surface of the housing 86 the contacts are urged against and intoelectrical contact with the electrodes 96, 98 by elastic spring tensionin the spring fingers 136.

As shown in FIGS. 13 and 14, a spring finger 136' includes a multi-tinedcontact 146 in place of the down-turned contacts 138 of the springfingers 136 just previously described. Each tine 148 has a length of,for example, about 0.06 cm, long enough to extend through the outerlayer 126 and inner layer 106 of the disposable absorbent sensormaterial 95 to make electrical contact with the electrodes withouthaving to be inserted within the tubes. This construction permits theabsorbent sensor material of the disposable sensing pad to be used topresent the adhesive 102 facing in a desired direction with respect tothe housing 86, to attach the sensing pad 94 either to a patient'sundergarment or to a patient's skin, depending upon the application forwhich the body fluid detecting device 80 is being used. Alternatively,the tines, electrically connected, could be provided on the housing 86with the spring fingers 136 pressing the electrodes into contact withthe tines.

Certain people, because of medical conditions, are unable to detectnormally and reliably when uncontrollable urination is about to begin.In some of such people, however, a small amount of urine, great enoughto be detected by a sensing device according to the invention, leaksfrom the person early enough for the person, if aware of such leakage,to proceed to a toilet to complete voiding the bladder. Such persons canutilize a body fluid sensing device 150 including a vibrator 152 as itssignaling device as shown in FIGS. 15 and 16. The vibrator 152 iscontained within a housing 154 similar to the housing 86, and can befelt by the wearer, allowing the person wearing the device to proceed toa restroom soon enough to avoid embarrassment by wet clothing. Thedevice 150 itself does not cause embarrassment, however, because itssignal is inaudible to nearby people. This permits the person with sucha medical problem to live in a substantially normal way, without havingto be catheterized or to wear diapers. A suitable vibrator circuit,shown in FIG. 16, includes a TLC 555 integrated circuit available fromTandy Corporation, of Dallas, Tex., which, when connected as shown,latches in a mode providing power to the vibrator 152 once conductivityis established, even briefly, between the spring fingers, as by urineproviding a conductive path between electrodes 96, 98 of a disposablesensing pad 94 connected to the contacts 138 of the spring fingers 136of the housing 154. A suitable vibrator 152 is a vibration pager Model7CE-1701 WL-00, available from Namiki Precision Jewel Co., Ltd., ofRochelle Park, N.J., which includes a small coreless DC motor and aneccentrically weighted shaft.

A reusable sensor 18 or a disposable sensor 94 according to the presentinvention may be used in a system containing one or more of the sensingdevices, each equipped with a small, low-powered radio transmitter andone or more receivers and display devices, to monitor, for example,infants, invalids, or nursing home or hospital patients suffering from,among other things, urinary incontinence, pressure sores, surgicalwounds, and other problems.

For example, as shown in FIG. 17, in one basic form of such a system, atransmitter included in body fluid detecting device 160 connected with asensing pad 94 (or with a reusable sensor 18) transmits at very lowpower on a frequency within the commercially used FM broadcast band.When an electrically conductive fluid completes the electrical pathbetween electrodes of the sensing pad 94 the transmitter begins totransmit, continuing to transmit a signal until an FM receiver in theclose vicinity, as within the same house, for example, alerts a personwho can disconnect the device from the electrodes of the sensing pad 94,or until the battery powering the transmitter is exhausted. Preferably,the transmitting frequency is variable to avoid local commercialbroadcast frequencies. A timing circuit could be connected to thetransmitter (as in the circuit shown in FIG. 19) to limit battery drain.

A receiving device for use with such a transmitter for a single patientsituation may simply be an ordinary household FM receiver 162, so that acaregiver could keep several receivers tuned, in different locations inthe house, to receive a signal indicating that attention to the patientis required, or may carry a small portable FM receiver tuned to providethe signal no matter where the responsible person moves within thetransmitting range of the device.

Another receiver device, as shown in FIG. 18, may be a special-purposereceiver 164 including an audible signaling device 166 or visiblesignaling device 168. A latch circuit is included to turn on thesignaling device and keep it activated until turned off or reset by theresponsible person.

A body fluid detecting device 170 which is another embodiment of theinvention incorporates a circuit as shown in FIG. 19, and controls atransmitter 172 to provide an FM radio signal which is transmitted foronly a limited time, for example one second. The transmitter 172 isreactivated periodically to send another such transmission, with a delaybetween transmissions which is established by the value of the resistorR_(T). For example, when R_(T) is 10 megohms, the delay is two minutes,and when R_(T) is 20 megohms the delay is four minutes. (If a firstencoded signal transmission is not received by the receiver 164, thenext or a subsequent transmission is received by the special purposereceiver 164 and the signaling device 166 is activated and latched"on.") The included transmitter 172 is accompanied by a digital encodingdevice which uniquely identifies the transmitter of the device 170. Atransmitter test switch 174 and an indicator lamp 175 which are alsoprovided.

Where there are multiple patients to be monitored, as in a hospital ornursing home, a central receiving device may be used with severalsensing devices 170. Referring now to FIGS. 20 and 21, the nursesstation 176 includes an internal computer 178 and an RS-232 interface180 through which inputs and outputs to and from an external computer183 may be directed. The station 176 includes a printer 182 on which theidentity of each transmitter 172 of a sensing device 170 and the time oftransmission of an incident message signal (indicating a circuitcompleted through sensor electrodes) or a reset message (indicating useof the transmitter test switch 174) initiates a transmission which isreceived by the antenna 184. The antenna 184 may be more or lessefficient, depending on the needs imposed by the size of the building inwhich the system is used. An alarm circuit 186 responsive to signalsfrom the computer 178 provides an audio alarm signal 188 and illuminatesan indicator lamp 190 to show that a signal has been received. Controlcircuits 194 connected to the printer computer interface allow aprogramming circuit 196 to assign identification of patients totransmitters, each of which has its own unique encoded identificationsignal which is transmitted as a part of the transmitter protocol eachtime the transmitter of a body fluid sensing device such as the device170 is activated. A visual numerical display 198 provides an identifyingdisplay of the origin of the latest received transmission.

A receiver-decoder 200 receives each transmission and passes on thesignificant portion of the encoded identification signal to be processedthrough the control circuit 194 into the internal computer 178. Theseelements are included in a work station receiver available from LinearCorporation of Carlsbad, Calif. as its Linear Model AC-680 receiver,which operates in conjunction with and in response to Linear ModelACT-1/318 transmitters, each enclosed in an individual housing connectedto a respective sensor such as an appropriate length of the disposableabsorbent sensor material 95, or an appropriately-shapedelectrode-carrying member 34 provided with a pair of electrodes 44, 46and a corresponding sleeve 58 such as those included in the bed-wettingdetection device 10 described previously, or modified in size and shapeto be appropriate for sensing body fluids exuded from surgical woundsand the like or body discharges from animals, where the device is usedin a veterinary application.

Data accumulated in the internal computer 178 may be transmitted throughthe RS-232 interface 180 to the external computer 183 for assembly andcalculation of statistical data, filing and retrieval, and correlationwith other data concerning individual patients or groups of patients. Inparticular, computer-recorded photographs and medical histories ofpatients may be stored in a database for retrieval to evaluate patientprogress and efficiency of patient care and caretaker response to bodyfluid loss as shown by time of receipt of incident messages and resetmessages.

An alternative disposable sensing pad shown in FIGS. 22-25 may be formedas a rolled elongate strip of sensing pad material 202 which may be cutto length as desired in the same fashion as the disposable sensing pad94 previously described. The sensing pad material 202 includes a layer204 of an adhesive material, suitable for fastening the sensing padmaterial 202 to the inside of a garment, on a first face 205. Areleasable cover sheet 206 protects the layer 204 of adhesive materialso that the sensing pad material 202 can be stored as a roll yetunrolled easily and cut to a desired length for use in the same manneras is the sensing pad 94 in the fluid sensing device 84.

The sensing pad material 202 is preferably made from a two-ply laminatematerial 208, shown in FIG. 23, which includes a first layer 210 that isrelatively thin and through which liquids may pass easily. The firstlayer 210 may be made of a paper-like material, and preferably is anon-woven carrier sheet of synthetic fibers bonded; together, forexample by heat or chemical adhesives, into a thin, flexible, strong,and porous sheet, about 0.005 inch thick and with a weight of 14-20g/m², and preferably about 18 g/m². A second, or inner layer 212 isrelatively thick, with a thickness 213 of about 0.020-0.030 inch, forexample, and preferably has a fluffy, resilient texture. The layer 212is preferably made of a highly fluid-absorbent material which need notbe particularly strong, but which may include a distributed quantity ofmaterial to help the layer 212 to be bonded thermally, as by the use ofultrasonic welding equipment. The layer 212 may thus include a quantityof a latex material intermixed with a larger quantity of cellulose woodpulp fiber material, or, preferably, the layer 212 may be an air-laidpulp layer of a mixture of cellulose fibers and thermally bondablesynthetic fibers such as synthetic bicomponent fiber of polyethylene andpolyester, adhering to a layer 210 of a non-woven fiber such aspolyethylene, polypropylene, or a mixture of them which may be thermallybonded ultrasonically. Such a laminated material is available, forexample, from Merfin International, Inc. of Delta, B.C., Canada as itsproduct 40800N00 which has a weight of about 80 g/m²,

The laminated material 208 is preferably used in manufacture of thesensing pad material 202, in the form of a long strip having parallellateral margins 214 and 216 separated by a predetermined width 218, forexample 4 5/8 inches.

As shown in greater detail in FIG. 24, the sensing pad material 202defines a pair of separate tubes 220. Electrodes 222 and 224 are eachlocated within a respective one of the tubes 220. The electrodes 222,224 may each be 3/8 inch wide, for example, and each electrode 222, 224is attached by a respective layer of adhesive material 226 to an exposedsurface of the inner layer 212. Each electrode 222, 224, shown withexaggerated thickness in FIG. 24, is generally ribbon-like and ispreferably of a synthetic plastic material such as a Mylar™ polyesterstrip 228 having layers of electrically conductive material adheredthereto, preferably on both sides as layers 230, 232, although it wouldbe possible to omit the electrically conductive layer from one side.Preferably, the strip 228 is thin enough to be easily flexible, having athickness 234 of, for example, 1 1/2 mils. The layers of conductivematerial 230, 232 may, preferably, be evaporatively deposited aluminumhaving a thickness in the range of about 100-200 Angstroms, for example.Preferably, the layer 226 is a thin interrupted layer of hot meltadhesive applied in a pattern using conventional equipment, and thelayer 232 of conductive material is thus available for electricalcontact such as by the tines 148 extending through the outer layer 210,the inner layer 212 and the layer 226 of adhesive.

The electrodes 222 and 224 extend parallel with each other separatedfrom each other by a distance defining a central area 236 between theelectrodes 222 and 224. The lateral margins 214 and 216 of the laminatematerial 208 are folded toward the central area 236 defined between theelectrodes 222 and 224 and abut against each other, or, alternatively,may be overlapped, in the central area 236. A narrow portion of thelaminate material 208 extending along each of the lateral margins 214and 216 is fastened to the laminate material 208 within the central area236, to form the separate tubes 220.

The electrodes 222 and 224 are thus each enclosed within a respectiveone of the tubes 220 separately, and the conductive material 230 on oneface of each of the electrodes 222 and 224 is free from the overlyingsurface of the portion of the inner layer 212 adjacent the respectivelateral margin 214 or 216. The tubes 220 can thus easily be expanded toreceive a contact (such as the contacts 138 shown in FIG. 8) extendinginto an end of each tube 220 to rest upon and make electrical contactwith the electrically conductive material 230 of a respective one of theelectrodes 222 and 224 for use of the sensing pad material 202.

As shown in FIGS. 22 and 24, the strips of material adjacent the lateralmargins 214 and 216 are attached to the central area 236 by thermalwelding, as by the use of an ultrasonic welder. A strip of an adhesivematerial 238 could also be used, as shown in FIG. 25 to effectattachment of the narrow portions of the laminate material 208 adjacentthe lateral margins 214 and 216 to the central area 236.

According to the invention, the process of manufacturing the elongatestrip of sensor material 202 may be carried out as shown in FIGS. 26 and27, using the equipment shown in FIG. 28, for example. Accordingly, as afirst step 240, a roll of laminate material 208 is slit to a desiredwidth, for example, 4 5/8 inch wide, and made ready as a supply roll 242(FIG. 28).

Subsequently, in step 244 shown in FIG. 26, the electrodes 222, 224,which are preferably supplied from horizontally mounted reels 246, arefed beneath the nozzle 248 of a hot melt glue dispensing system 250 suchas a programmable hot melt glue dispensing system available from theNordson Corporation of Atlanta, Ga. to deposit a pattern of glue as thelayer 226 on each of the electrodes 222, 224. The electrodes are thenled into the appropriate positions atop the inner layer 212, as shown at252, where a roller 254 presses the electrodes 222, 224 into contactwith the inner layer 212.

A photo-optic electronic steering station 256 observes the position ofthe lateral margins 214, 216 and applies pressure through a servo-systemas necessary to steer the strip of laminate material 208 and attachedelectrodes 222, 224 to direct them into a three-stage folding station258, to perform step 260 shown in FIG. 26. In the folding station 258the outboard portions of the strip of laminate material 208 are foldedprogressively upward, around and into alignment with the central area236 between the electrodes 222 and 224, bringing the lateral margins 214and 216 into abutment with each other above the central area 236.

The folded laminate material 208 is progressively moved further to passthrough an ultrasonic stitcher 262 such as, for example, a Branson ModelFS-90 ultrasonic stitcher, available from Branson UltrasonicsCorporation of Danbury, Conn., which ultrasonically welds the lateralmargins 214 and 216 to the central area 236 to form the separate tubes220, thus forming effectively useable sensing pad material 202. Thesensing pad material 202 is then drawn further through an appropriatetension-regulating device 264 and into position for attachment of thelayer of adhesive material 204, together with and supported by the coversheet 206, provided from a continuous spool at 266.

The completed sensing pad material 202, with the adhesive layer 204 andcover sheet 206, is drawn continuously by a set of rubber drive rollers268 driven by an electric motor and equipped with a measuring devicesuch as an optical disc encoder programmable to control operation of anair-operated guillotine clipper 270 to cut the product into strips of adesired length for packaging and retail sale, either in the form of aspool from which lengths of chosen lengths may be cut by the consumer,or in the form of pre-cut ready-for-use fluid-absorbent sensor pads.

A suitable adhesive 204 and cover sheet 206, in a form allowingsimultaneous application from a single spool of material, are availablefrom 3 Sigma, a Division of Anchor Continental, of Columbia, S.C., asits No. 93004 adhesive tissue garment tack with 2-inch-wide releasepaper.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

What is claimed is:
 1. A sensing pad for use in detecting the presenceof electrically conductive fluids, the sensing pad comprising:(a) afirst layer, of a flexible sheet material; (b) a pair of elongateflexible electrodes extending generally parallel with and spaced apartfrom each other and attached to said first layer, each of saidelectrodes having a medial longitudinal margin and a laterallongitudinal margin; and (c) a second layer, of fluid-absorbent flexiblesheet material overlying said electrodes and adhered to said first layeralong a continuous central strip extending parallel with said electrodesand located between said electrodes, said second layer also beingconnected to said first layer along a respective portion extendingparallel with said electrodes and located alongside said laterallongitudinal margin of each of said electrodes, said first and secondlayers thereby constituting a pair of separately defined parallel tubesattached to each other along a length of each, with each of said tubesincluding one of said electrodes, each of said electrodes having arespective electrically conductive surface exposed within the respectiveone of said tubes and each of said electrodes being prevented by saidseparate parallel tubes from touching said electrically conductivesurface of the other flexible electrode of said pair.
 2. Apparatus fordetecting the presence of electrically conductive fluid, comprising:(a)a first layer, of a flexible sheet material; (b) a pair of elongateflexible electrodes extending along said first layer generally parallelwith and spaced apart from each other, each of said electrodes of saidpair being attached to said first layer and having a medial longitudinalmargin and a lateral longitudinal margin; (c) a second layer, offluid-absorbent flexible sheet material overlying said electrodes andadhered to said first layer along a continuous central strip extendingparallel with said electrodes and located between said electrodes, saidsecond layer also being connected to said first layer along a respectiveportion extending parallel with said electrodes and located alongsidesaid lateral longitudinal margin of each of said electrodes, said firstand second layers thereby constituting a pair of separately definedparallel tubes attached to each other along a length of each, with eachof said tubes including one of said electrodes, each of said electrodeshaving a respective electrically conductive surface exposed within therespective one of said tubes and each of said electrodes being preventedby said separate parallel tubes from touching said electricallyconductive surface of the other flexible electrode of said pair; and (d)signaling means connected electrically to said electrodes, for producinga signal in response to electrical resistance between said electrodesbeing below a predetermined value.
 3. The apparatus of claim 2 whereinsaid signaling means includes a vibrator for producing said signalinaudibly.
 4. The apparatus of claim 2 wherein said signaling meansincludes means for providing said signal visibly.
 5. The apparatus ofclaim 2 wherein said signaling means includes means for providing saidsignal in an audible form.
 6. The apparatus of claim 2 wherein saidsignaling means includes a wireless transmitter.
 7. The apparatus ofclaim 2 wherein said signaling means includes means for producing andtransmitting a machine-intelligible message.
 8. The apparatus of claim2, including a housing containing said signaling means, and furtherincluding a spring finger mounted on said housing, said spring fingerincluding a contact located thereon, said contact pressing against oneof said electrodes and thereby connecting said one of said electrodeselectrically with said signaling means.
 9. The apparatus of claim 8,including a lever-operated release cam associated with said springfinger.
 10. The apparatus of claim 8, including a tine associated withsaid contact, for piercing at least one of said first and second layersand electrically contacting said electrode.
 11. The apparatus of claim 2wherein said signaling means includes a timer limiting the duration ofsaid signal to a predetermined time.
 12. A sensing pad for use indetecting the presence of electrically conductive fluids, the sensingpad comprising:(a) a sheet-like layer of absorbent material; (b) a pairof elongate ribbon-like electrodes, each having a conductive surface,both of said electrodes being adhered to said layer of absorbentmaterial in respective apart-spaced locations, thereby defining acentral area therebetween, respective lateral portions of said layer ofabsorbent material being interconnected with each other in said centralarea, thereby defining a pair of tubes, each separately enclosing arespective one of said electrodes.
 13. The sensing pad of claim 12wherein at least a part of said conductive surface of each of saidelectrodes is exposed and free from said layer of absorbent material.14. A sensing pad for use in detecting the presence of electricallyconductive fluids, the sensing pad comprising:(a) a fluid-permeable,flexible outer layer; (b) an inner layer of absorbent material supportedby said outer layer; (c) a pair of elongate electrodes, each having aconductive surface, both of said electrodes being adhered to said innerlayer of absorbent material in respective apart-spaced locations,thereby defining a central area therebetween, respective portions ofsaid outer layer being interconnected with each other in said centralarea and respective portions of said inner layer being interconnectedwith each other in said central area, thereby defining a pair ofseparate tubes, each enclosing a respective one of said electrodes. 15.The sensing pad of claim 14 wherein at least a part of said conductivesurface of each of said electrodes is exposed and free from said innerlayer of absorbent material.
 16. The sensing pad of claim 14 whereinsaid outer layer is of non-woven sheet material.
 17. The sensing pad ofclaim 14 wherein said outer layer is a sheet of bonded synthetic fibers.18. The sensing pad of claim 14 wherein said inner layer is of fluffy,soft material including cellulose fibers.
 19. The sensing pad of claim14 wherein at least one of said layers includes a quantity of materialenabling said layers to be thermally bonded to form said tubes.
 20. Thesensing pad of claim 14 wherein said outer and inner layers are adheredto each other as a single two-ply sheet of material.
 21. The sensing padof claim 14 wherein lateral margin portions of said outer and innerlayers are folded inwardly around said electrodes and adhered to saidcentral area.
 22. The sensing pad of claim 21 wherein said lateralmargin portions are adhered to each other and to said central area bythermal welding.
 23. The sensing pad of claim 14 wherein respectivelateral portions of said outer and inner layers are folded inward aroundsaid electrodes and interconnected with each other by a layer ofadhesive material located in said central area.
 24. The sensing pad ofclaim 14 having a portion of said outer layer defining a first face anda layer of an adhesive material overlying said outer sheet on said firstface.
 25. The sensing pad of claim 24 including a releasable coveroverlying said layer of adhesive material on said first face.
 26. Thesensing pad of claim 14 wherein said electrodes are of flexiblesynthetic plastic sheet material coated with electrically conductivematerial.
 27. The sensing pad of claim 26 wherein said electrodes eachinclude a conductive surface exposed and unattached inside a respectiveone of said tubes.
 28. The sensing pad of claim 14 wherein each of saidelectrodes includes layer of electrically conductive metal foil having asurface exposed and unattached inside a respective one of said tubes.29. A method of manufacturing a sensing pad for use in detectingelectrically conductive fluids, the method comprising:(a) providing anelongate sheet of fluid-absorbent material having a pair of parallellateral margins; (b) attaching a pair of electrodes to said sheet ofmaterial parallel with each other and on opposite sides of a laterallycentral longitudinally extending central portion of said sheet,extending parallel with said lateral margins; (c) folding said materialto extend around said electrodes and to bring said lateral marginstogether; and (d) attaching said lateral margins to said laterallycentral portion between said electrodes, thereby defining a pair ofadjacent tubes, each having an inner face and a respective one of saidelectrodes attached to said inner face.
 30. The method of claim 29wherein said elongate sheet of material includes a relatively strong andthin flexible fluid-previous outer layer and a relatively thick innerlayer of fluid-absorbent material.
 31. The method of claim 29 includingthe step of using an adhesive material for attaching said lateralmargins to said laterally central portion.
 32. The method of claim 29including the step of using sonic welding for attaching said lateralmargins to said laterally central portion.
 33. The method of claim 29including the step of overlapping said lateral margins adjacent to saidlaterally central portion between said electrodes.